Java Wrapper Class Example

Advertisement

Java Wrapper class example explains you the use of various wrapper classes.

Java Wrapper Class Example

In this section we will read about how to use the wrapper classes in Java.

Wrapper classes wrap the primitive data types to objects of that class. In
Java there are eight primitive data types and each data type has the
corresponding wrapper class. These wrapper classes belongs to the java.lang
package. In Java the wrapper classes are required to allow the null values
because objects can be null whereas, the primitives can't. Wrapper classes are
used in to include the values in Collection, it is required for type safety. It
is required when treating the primitives values as an object with other objects.
The table given below lists the primitive data types and its respective wrapper
class :

Primitive Data Type

Wrapper Class

boolean

Boolean

byte

Byte

char

Character

int

Integer

float

Float

double

Double

long

Long

short

Short

Following image demonstrates the hierarchy of the Wrapper class :

Almost all of each wrapper class has the parseXXX(), toString(), xxxxValue()
etc. Below we are discussing some of the methods of java.lang.Integer class but, these
methods are usually applies on almost all wrapper classes.

Method Name

Method Description

parseInt(String s)

This method is used to parse the String representation of number to signed
decimal integer.Syntax : public static int parseInt(String s) throws
NumberFormatException

toString()

This method is used to represent an Integer value to a String object.Syntax : public String toString()

valueOf(String s)

This method is used to represent the value of String as an Integer object.Syntax : public static Integer valueOf(String s) throws
NumberFormatException

equals(Object obj)

This method is used to compare the object with the specified object whether
they are equals or not.Syntax : public boolean equals(Object obj)

hashCode()

This method is used to find the hash code of the Integer.Syntax : public int hashCode()

compareTo(Integer anotherInteger)

This method is used to compare two Integers. It returns 0 (zero) if the
values are equal, returns negative value if the specified object value is
greater than the invoking object vlaue, returns positive value if the specified
object value is lower than the invoking object value.Syntax : public int compareTo(Integer anotherInteger)

compareTo(Object o)

This method is used to compare the Integer object to another object.Syntax : public int compareTo(Object o)

Example

Here I am giving a simple example which will demonstrate you about how to use
the wrapper classes in Java. In this example we will create a Java class where
we will use the various methods of java.lang.Integer class such as compareTo(),
equal(), toString() etc.